The Supreme Court held that determining the results of a natural correlation using well-understood, routine, conventional steps, as per the appealed claims here, amounted to simply telling doctors to apply the natural law, identifying that "a scientific truth, or the mathematical expression of it, is not a patentable invention." Id. at 71 (quoting Mackay Radio & Telegraph Co. v. Radio Corp. of Am., 306 U.S. 86, 188 (1939)), 79.